A. Field of the Invention
The present invention relates generally to valves, and more particularly to valves which in normal operation can be moved between open and closed positions, but which, when exposed to a selected high temperature level, will automatically be moved to a selected one of the open or closed positions and to an energy storing assist device for aiding in said movement.
B. Description of the Prior Art
In many instances, it would be desirable to utilize a valve which, under normal circumstances, could be readily opened and closed to perform its normal valving function, but upon exposure of such valve to excessively high temperatures, as for example, temperatures developed in fires, the valve would actuate fully to a selected one of its open or closed positions. For example, such a valve could be used in refineries, chemical plants and the like as well as in Christmas trees and flow lines in producing oil and gas wells to be automatically closed in the event of a fire as a safety precaution and to prevent the fluid normally flowing through such valve from further feeding the fire. Such heat sensitive valves would thus "fail" to the closed position. On the other hand, there may be instances where it would be desired for the valve to "fail" to the open position in the event of a fire. For example, it might be desirable to vent fluid to a flare in the event of a fire. As indicated, with either type of valve, it would be desirable to be able to utilize the valve as a normal valve during day-to-day operations in the sense that the valve could be readily opened and closed at will.
In co-pending U.S. patent application Ser. No. 416,686, filed Sept. 10, 1982, which is now U.S. Pat. No. 4,421,134 there is disclosed a heat sensitive gate valve, which under normal conditions, operates as a manual valve by rotation of a handwheel. The valve includes a fusible element, which when exposed to excessive heat as in a fire, allows valve body pressure acting on the valve stem to force the stem and gate to the closed position. The valve of U.S. Pat. No. 4,421,134 is thus well adapted to meet the needs described above. However, if valve body pressure is less than a certain amount, the force generated by such pressure may not be sufficient to close the valve. In such circumstances, even after melting of the fusible element, fluid flow would continue at low pressures.
Accordingly, it is an object of the present invention to provide means for moving a fire-safe valve to the "fail" position irrespective of valve body pressure.
It is a further object of the present invention to provide a device which stores and retains a predetermined amount of energy sufficient to operate a fire safe valve.
It is a further object of the present invention to provide an energy storing and retaining device that is a compact unit that can be included on a new valve or installed readily on a preexisting valve.
It is a further object of the present invention to provide an energy storing device that releases energy to do work when exposed to a predetermined high temperature.
It is a further object of the present invention to provide an energy storing device that has a limited stroke, but has sufficient available energy throughout its entire stroke to completely operate the fire-safe valve after release, but which prevents danger to service personnel.